1. Field of the Invention
This invention relates to a process for the preparation of synthetic coking coal using solvent refined coal.
As is well known, coking coal is essential to the production of coke for iron manufacture and the demand therefor is very high as iron production is increasing at the present time. However, the world-wide reserves of hard coking coal are very limited as compared with non-coking or soft coking coal reserves, and they are becoming exhausted. Thus, to deal with this problem, the utilization of non-coking coal, soft coking coal or other low coalified materials which are found in relatively abundant quantities is strongly desired, and many efforts for manufacturing synthetic coking coal from such low coalified materials have been made. This invention provides one method therefor.
2. Description of the Prior Art
As a reformed coal from low quality coals, solvent refined coal (SRC) is known, as disclosed, for example, in U.S. Pat. No. 3,341,447 and in "Research and Development Report No. 9, Solvent Processing of Coal to Produce a De-Ashed Product", the Department of the Interior, Office of Coal Research (presently the Energy Research and Development Administration).
According to this patent and report, SRC is a low ash-low sulfur product obtained from solvent extraction of coal under hydrogen pressure, wherein the coal is generally subjected to hydrocracking at a temperature of about 400.degree. C. under a pressure of about 100 atm. in the presence or absence of a catalyst, such as Co--Mo or Fe based catalyst, and the non-dissolved residue is removed from the hydrocracked product (the de-ashing step).
Practical application of SRC is now under study and industrial production thereof has not yet begun. However, in the light of its excellent qualities, particularly its low ash-low sulfur content, it is expected that SRC will, in the near future, obtain wide acclaim as a clean fuel.
Ordinarily, SRC has the following general composition and properties:
______________________________________ Ultimate Analysis Items Percent by Weight Carbon (C) 85-94 Hydrogen (H) 4.0-6.5 Nitrogen (N) 0.5-20 Oxygen (O) 1.0-5.0 Sulfur (S) 0.1-1.0 O/C Atomic Ratio 0.015-0.040 Proximate Analysis Items Percent by Weight Fixed Carbon 41-45 Volatile matter 55-58 Ash content 0.1-0.5 Properties Softening point 85-150.degree. C ______________________________________
From the above, the features of SRC are summarized as follows:
(1) SRC has a high carbon content of about 85-94% by weight which is comparable to that of coking coal, and its O/C atomic ratio is lower than 0.04.
(2) SRC has higher hydrogen content, higher volatile matter and lower oxygen content than ordinary coal.
(3) SRC has a softening point of about 100.degree. C. or so.
(4) From any types of starting coal material (for example, even from low quality material such as brown coal), SRC products of similar composition or properties can be obtained. (This is more specifically described hereinafter with respect to Table I).
From the above analysis, it can be seen that SRC is considerably different from natural hard coking coal in that the former has a higher volatile matter and a lower softening point, as compared with the latter. Some examples of ordinary starting coals for the production of metallurgical coke are shown as follows:
______________________________________ Initial Volatile Melting Brand matter (wt. %) CSN Point(.degree. C) ______________________________________ Itmann (U.S.A.) 16-19 7-9 427 Wyco (U.S.A.) 16-18 8-9 403 Moss No. 3 (U.S.A.) 26-28 8-9 355 South Bullli (Australia) 21-23 5-6 410 Liddell (Australia) 37-39 5-6 385 Akabira (Japan) 40-42 4-5 334 ______________________________________
Thus, it is difficult to use SRC itself in the production of coke for iron manufacturing, but if its volatile matter is lowered and its softening point is raised by means of any suitable technique, it may be expected that a good coking material having quality equivalent to that of natural coking coal can be obtained. This invention is based on such consideration.